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How To Insulate A Garage Ceiling

Cecil C. from Long Island, NY wrote:

Hi Itchy,

My unattached garage already has the walls insulated. What's the best way to insulate the ceiling using fiberglass batts?

You'll need to measure the length and width of the garage ceiling. This can be done from the floor as they are usually the same in size. Multiply your figures to come up with the square footage needed. You also want to measure the width between the joists to determine the correct width of insulation to buy. Next you need to measure the size of the joists to determine the thickness and R-Value you'll be able to use. Most garage ceilings are insulated with R-25 insulation, which will fit into a joist cavity of 8". If your joists are 10" deep you could opt for R-30. Check your local building code to determine if a vapor barrier is required for your area. If so, you'll need kraft faced batts.

You'll need: Fiberglass batts, staple hammer with staples, twine, ladder and utility knife.

Wearing protective gear, start in one corner of the garage. Begin placing the batts into the ceiling cavities. If you're using kraft paper batts make sure the paper side is facing the garage floor. Secure these as you go by stapling the flanges to the bottom of the joists. Some of the runs may be wider, requiring you to cut an additional strip of insulation to place into the cavity. When making cuts, it's best to use a piece of plywood rather than the garage floor as it will dull your blade. Use scrap insulation to fill any gaps or spaces in the insulated garage ceiling.

Skip this final step if you used kraft paper batts. The insulation needs to be secured. Using twine and your staple hammer, attach the twine along each run by stapling it to the bottom of the joists, every 8" in a shoelace pattern. Continue this process until the entire garage ceiling has been twined.

Related Tips and Advice:

How To Insulate Garage Walls
How To Install Blown In Insulation In Your Attic
How To Insulate A Concrete Wall
How To Insulate Ducts